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Astrophotography

Mars Odyssey Pays Early Dividends

Martian cliffs and canyons are seen glowing at thermal-infrared wavelengths in the dead of night. Bright areas are rocks giving off warmth that was absorbed during the day; darker areas are flat mesas covered with insulating sand and dust. The narrow, straight canyons are about 2 kilometers wide.

Courtesy NASA/JPL/Arizona State University.

After a six-month flight from Earth and three months of tricky aerobraking to settle into a low orbit, NASA's 2001 Mars Odyssey spacecraft has begun bringing the agency some much-needed Martian success. On March 1st project scientists proudly showed off images and other data acquired by the craft since kicking off its 2½-year science mission two weeks ago.

One picture, taken through filters at nine infrared wavelengths, inaugurated the assaying of Martian surface minerals by the Thermal Emission Imaging System. THEMIS will map the entire planet at 100-meter resolution, 30 times more sharply than ever before, with a particular emphasis on minerals that can form only in the presence of water. Other infrared pictures shown on Friday, taken both in daylight and in the dark of night, sharply distinguish rocky from sandy terrain.

THEMIS is also taking pictures in visible light. These resolve features as small as 18 meters across, which is not as detailed as the ultrasharp images still being amassed by the orbiting Mars Global Surveyor. But the latter cover only a small fraction of the Martian surface, whereas Mars Odyssey's will eventually cover the entire planet.

A swath of Terra Sirenum seen in thermal infrared emission by day. Bare rock now appears black, absorbing more of the Sun's heat than it emits; dust and sand are light. The dark rims around relatively young craters are boulder fields of ejecta. Other brightness differences indicate temperature variations between Sun-facing and shadowed slopes. The largest crater at lower left is about 2 kilometers wide.

NASA/JPL/Arizona State University.

Mars Odyssey carries two other primary instruments. The Gamma Ray Spectrometer (GRS) will map about 20 chemical elements to depths of a few feet underground, though with only 250-kilometer resolution. Scientists are especially eager to turn up areas with buried hydrogen, a sign of water ice that could be mined by future astronauts. And the news is already very positive: water appears to permeate a large area of the planet's southern hemisphere. Investigator William Boynton (University of Arizona) reports that a strong hydrogen signal was immediately found within 30° of the south pole, an area roughly the size of Europe.

Last is the Mars Radiation Environment Experiment (MARIE), intended to study radiation that could endanger humans on Mars and in interplanetary space. MARIE went silent last August, but ground controllers still hope to fix it.

Mars Odyssey will also act as a communications link for future missions, including NASA's Exploration Rovers to be launched in 2003.

Planetary scientists have good reason to be elated with the craft's early success. Of NASA's five previous Mars missions in the last 20 years, three failed completely or crashed on arrival.

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